Multilayer capacitors are known from the publication by M. Valant and D. Suvorov: “Microwave Ceramics with Permittivity over 400,” The 9th International Meeting on Ferroelectricity, Seoul, South Korea, 1997, Abstract Book, P-05-TH-067, the dielectric layer of which has a ceramic based on a niobium-based perovskite-type “solid solution” having the general formula A(B1-xNbx)O3. It has been found that such ceramics are characterized by a high dielectric constant, ε=400. In addition, these ceramic materials have suitable dielectric properties at low frequencies, between 100 kHz and 1 MHz, so that they are suitable for use in multilayer capacitors.
A ceramic material is known from the publication by A. Kania: “Ag(Nb1-xTax)O3 Solid Solutions—Dielectric Properties and Phase Transitions,” Phase Transitions, 1983, Volume 3, pp. 131 through 140, that is produced on the basis of silver, niobium, and tantalum, hereafter called ANT, and is present in the form of a “solid solution” of the two materials AgNbO3 and AgTaO3. The ceramic described in this publication has the composition Ag(Nb1-xTax)O3, called ANTx in the following, where x can vary between 0 and 0.7. Depending on the composition, this ceramic has an ε between 80 and 400 at a temperature of about 300 K.
It is known from the publication by Matjaz Valant and Danilo Suvorov: “New High-Permittivity Ag(Nb1-xTax)O3 Microwave Ceramics: Part 2, Dielectric Characteristics,” J. Am. Ceram. Soc. 82[1], pp. 88–93, (1999), that disk-shaped ceramic bodies of ANTx with an x-parameter between 0.46 and 0.54 have a strong relative change in the dielectric constant, ε, in the temperature range between −20° C. and 120° C. It was shown there, in particular, that the course of the relative change in ε with temperature follows a curve that has a maximum between 20° C. and 70° C. and takes on values between −0.07 and 0.01. The dielectric constant, ε, in this case is between 360 and 415, depending on the tantalum content of the ceramic.
Multilayer capacitors are known from the reference DE 196 53 792 A1, in which the dielectric layers consist of various ceramic materials, whereby different temperature coefficients can balance one another. These capacitors have the disadvantage that in order to produce them, a variety of ceramic materials must be created and a higher cost is consequently necessary. On the one hand, the ceramics used for this are based partly on strontium titanate and partly on strontium titanate with alloys (TCC negative). On the other hand, materials with positive temperature coefficients for capacitance based on tantalum oxide manganese titanate are used as dielectrics.
It is also known from the reference WO 98/03446 that by doping ANT with lithium, tungsten, manganese, or bismuth, the temperature coefficient of the dielectric constant, TCε, can be reduced to very small values of ±70 ppm/K° at specific temperatures.
The known multilayer capacitors have the disadvantage that the ceramics used in the capacitor have a relatively small dielectric constant. This has the consequence that in order to produce capacitors with high capacitances, relatively large component sizes are required. This is undesirable due to the advancing miniaturization of electrical components, especially in the cell phone sector.